1. Field of the Invention
The present invention relates to the optical switch used in the optical communication system, especially to the micro-optical switch having fine mirror capable of biaxially rotating and the method for manufacturing the same.
2. Description of the Prior Art
As the demand for the optical communication network is explosively increasing, researches for MEMS (micro-electro-mechanical systems) type optical switches with all-optical structure capable of transmitting information with faster speed and larger capacity are being conducted. The MEMS means the technique for making the electromotive devices small-sized and integrated. This MEMS technique can manufacture the small-sized devices on a semiconductor wafer with precision using the processes like lithography, deposition, etching, etc, thereby has advantage in accomplishing the multifunction.
Most conventional MEMS type optical switches use electrostatic force, piezoelectric force, or thermal expansion force and require high driving voltage or power dissipation, and in the case of using the piezoelectric force, problems occur in reliability to the device characteristics.
Meanwhile, in the case of using the magnetic force, structure of the optical switch can be simple, and high drive force and displacement can be obtained. To date, The type of optical switch capable of moving uniaxially due to a limitation of structure using electrostatic force together or Lorentz force has been devised. For example, Hiroshi Toshoyoshi""s xe2x80x9cElectromagnetic Torsion Mirrors for Self-Aligned Fiber-Optic Crossconnectors by Silicon Micromachiningxe2x80x9d issued in January, 1999, xe2x80x9cIEEE J. Select. Topics Quantum Electronxe2x80x9d shows the micro-electro-mechanical optical switch that drive the torsion mirror using an electromagnetic force as a driving force. Such an optical switch provides the technical idea like that the optical switch uses the silicon fine processing and is aligned at a micro mirror using self-alignment method, and the micro mirror drive corresponding to the magnetic field produced by a permanent magnet.
To use the Lorentz force, the direction of the wires flowing the current and the direction of the magnetic field must be perpendicular each other, and to get the biaxial degree of freedom, magnetic fields are perpendicularly crossed each other. But this causes a problem that a proper force can not be applied to the wire due to an interaction of magnetic fields.
Thus, the object of the present invention is to provide a micro-optical switch capable of driving biaxially by the magnetic field in one direction using the torsion hinge with 45xc2x0 to the magnetic field.
Other object of the present invention is to provide a method for manufacturing the micro-optical switch capable of driving biaxially by the magnetic field in one direction using the torsion hinge with 45xc2x0 to the magnetic field.
To achieve the object, A micro-optical switch according to the present invention comprises, an external frame having holes inside; an internal frame positioned in the holes and also having the holes inside; a light reflecting means positioned inside the holes of the internal frame; external magnetic substances positioned at both sides of the external frame; outside torsion hinge for connecting the external frame to the internal frame and having 45xc2x0 to the magnetic field produced by the external magnetic substances; inside torsion hinge for connecting the internal frame to the light reflecting means and for being perpendicular to said outside torsion hinge; outside coils wired in the internal frame; and inside coils wired in the light reflecting means, and the light reflecting means and the internal frame are preferably rotated by the inside torsion hinge and the outside torsion hinge as an axis when a current is applied to the inside coil and the outside coil.
To achieve the other object, A method for manufacturing the micro-optical switch according to the present invention preferably comprises, depositing the etching stopper film on the bottom surface of SOI wafer consisted of upper, medium, and lower layers; removing the etching stopper film except its region defining the external frame; depositing an insulating layer on the upper layer, and etching the insulating layer and the upper layer by using the mask defining the internal frame, light reflecting means, inside torsion hinge, and outside torsion hinge; forming the inside and outside coils on the insulating layer; depositing a protection layer on the upper surface of the structure formed by the aforementioned steps, and etching the lower layer using the etching stopper film as a mask; and removing the protection layer, and floating from the lower space of the SOI wafer the internal frame, light reflecting means, inside torsion hinge, and outside torsion hinge by etching the medium layer.